In the Twitch's Ambush (Q) it says at the bottom "If Twitch takes damage while casting Ambush, the stealth activation is delayed to 4.5 seconds."
But if I use heal it will do the same thing it will also cancel his stealth once the activation is complete and in stealth mode.
This I think this needs to change because heal is not taking away your HP, you are gaining HP from it.
Clearly it is coded as giving you negative damage or some such thing, or it could be that activating the summoner counts as an action, thus breaking stealth.
Meanwhile Rengar.
Does this work on all Stealth or just Twitch stealth? I know Twitch stealth has had some snags in the past, but I think heals shouldn't backfire like this situation.
Heal should probably not delay stealth, since it is indeed not damage.
On the other hand, damage doesn't break stealth. But most actions break stealth. The wiki mentions explicitly Teleport and Item Actives as breaking stealth. I don't see why Heal shouldn't break stealth also.
This happened to me once. I was trying to stealth and heal while stealthed against a vayne to bait her and win a 1v1, but it broke my stealth while I was re positioning and got me wall stunned. Smh.
Honestly the only thing twitch needs is on kills to increase the duration of his ult by 2 seconds. Miss Fortune took twitches niche of this Wombo ADC, and now twitch is in an awkward position. The other thing I would like to see is if twitch gets a kill ambush stealths him after 3 seconds regardless
agreed
I feel it is unfair for literally everything to cancel 
's stealth
Casting W and E disrupt/delay stealth right? Why would casting Heal not?
I'm ok with the heal and stuff breaking his Q, I just wish that minions shouldn't be able to delay it as well
Stupid realization: Heals are coded as negative damage.
More realistic analysis: TBH, I really think that all stealth should be broken by healing when the person doing the healing is themselves visible to the enemy team. It's not inherently obvious to new players that using a Sona or Soraka heal on someone immediately gives away their position, even if they are stealthed, and revealing a stealthed ally to the enemy team is almost never a good thing.
I believe this should fall into bug reports
Take Barrier. It also prevents him from getting damage before he is stealth, so unless the Barrier is completely broken, he gets stealthed after 1.5 seconds even if he is attacked.
